The Hero hitmaker was reportedly paid over $1 million for a two-hour concert on Sunday at a gala for the Angolan Red Cross, which was sponsored by bosses at mobile phone company Unitel and attended by the president.

The politician's daughter, Isabel, owns Unitel and is the head of the Angolan Red Cross.

Addressing the crowd at the event, Carey reportedly said, "I am happy to be here in this room and I am honoured to share this show with the President of Angola."

However, the lucrative gig, which occurred five years after she performed a controversial New Year's Eve show for late Libyan leader Moammar Gadhafi's family in 2008, has landed the singer in trouble with The Human Rights Foundation president, Thor Halvorssen, who claims Carey should have researched the allegations of corruption and human rights abuses against Dos Santos before accepting the job.

In a statement, Halvorssen describes Dos Santos as a "dictator", writing, "Mariah Carey can't seem to get enough dictator cash, reportedly more than $1 million this time. Just five years ago she performed for the family of Libyan dictator Moammar Gadhafi. Now, she goes from private performances to public displays of support and credibility for one of Africa's chief human rights violators and most corrupt tyrants.

"It is the sad spectacle of an international artist purchased by a ruthless police state to entertain and whitewash the father-daughter kleptocracy that has amassed billions in ill-gotten wealth while the majority of Angola lives on less than $2 a day."

Carey apologized for her Libyan gig after it sparked a backlash, but she isn't alone - Jennifer Lopez, Beyonce and Usher have all been criticized for staging similar performances for other controversial figureheads in the past.